High molecular weight poly (epsilon-caprolactone) (also known as "polycaprolactone"), various thermoplastic acrylics, and other heat-softenable materials have been used to take impressions of teeth or to make custom dental trays. References describing such thermoplastic compositions include U.S. Pat. Nos. 2,020,311, 4,227,877, 4,361,528, 4,401,616, 4,413,979, 4,569,342, 4,619,610 4,657,509, 4,659,786, 4,768,951, 4,776,792, and 4,835,203. Other references include Kokai (Japanese Published Pat. Appl.) Nos. Sho 63[1988]-96536 [which discloses oil-extended ethylene vinyl acetate ("EVA") copolymers that are stored in syringes before use]; Sho 63[1988]-171554 and Sho 63[1988]-270759; and TONE.RTM. POLYMERS P-300 AND P-700 High Molecular Weight Caprolactone Polymers (1988 product literature of Union Carbide Corp.). In the main, the thermoplastic materials of these references are used without a surrounding shell, or their manner of use is not specifically described. In some instances the thermoplastic materials are themselves shaped to form a custom tray which is in turn used as a shell surrounding a conventional non-thermoplastic elastomeric impression material such as a polysiloxane. The thermoplastic materials of the '610 and '792 patents are exceptions; both employ a thin thermoplastic sheet surrounded by a rigid tray. In each of these latter two patents (and in the "OCCLUSAL HARMONY" dental tray from Advantage Dental Products, Inc., a commercial version of the tray shown in the '792 patent) the thin thermoplastic sheet is used to make a bite registration of only the occlusal tooth surfaces.
Other commercially available dental impression trays that contain a heat-softenable thermoplastic include the "EASY TRAY" from Oral Dynamics Inc. Division of Anson International, the "HEAT FORM" tray from Shofu, Inc., and the "AQUERON" custom tray from Erkodent Company. These latter three products are heated and shaped to conform to the shape of a patient's dental tissue, then typically filled with elastomeric impression material and reinserted in the patient's mouth to take an impression of the dental tissue.
There are only a few preloaded impression trays (trays intended to be sold with the impression material in the tray) described in the dental literature. U.S. Pat. Nos. 4,553,936 and 4,867,680 describe preloaded trays containing light-curable acrylic impression materials. The impression materials are not said to be thermoplastic. Instead, they apparently are flowable or pourable at room temperature, and are held in the tray using a flexible cover sheet or skin material.
Kokai Hei 2[1990]-45049 describes an impression technique that employs a thermoplastic propionic cellulose acetate impression material that is heated in a rod shape, bent to conform to an arch-shaped tray, "piled" on the tray, and inserted into a patient's mouth while still warm. The tray is not a preloaded dental impression tray, in that the impression material resides in the tray for only a short time before it is inserted in a patient's mouth, and is not intended to be sold in preloaded form.